1. Field of the Invention
The present invention relates to a method and apparatus for blow molding plastic containers and the like and for removal of unwanted flash material therefrom, and particularly to molding of the dome portion and tail portion of the containers to facilitate removal thereof.
2. Description of the Prior Art
In the process of molding bottles or other containers, the articles are formed from an extruded parison held between a pair of mating mold halves. After forming of the article, the mold halves are separated and the molded article ejected. It is common for flashings, which refers to a fin-like web projecting from the surface of the material, to be formed at the parting line across the bottom of the bottle or container where the mold halves are in engagement. It is also common for a ball-like dome to form at the top of the container above the neck. These flashings must then be removed in a separate operation, either by hand or by automatic machines.
While there are many devices and apparatus for removing flashings, the most common approach is to utilize mating dies that grip around the neck of the container and at the bottom of the container. When such dies are used, the container must be rigid to be able to remain its shape under the force of the dies. Immediately after molding of the container, the plastic material remains in a softened condition and therefore it is necessary to cool the container before conventional trimming operations can be accomplished. The storage, handling, and entering of containers in an automatic machine utilizing dies requires additional space and costs. Such equipment is relatively expensive since the dies must be matched to the shape of the container in production.
Machines have been developed in the prior art for trimming bottles or containers while still hot but which have required specific jigs to hold an individual bottle during trimming. For example, in U.S. Pat. No. 3,795,162 to Jaeger, a milk container is held by its neck and handle while a swinging arm cuts the tail flashing from the bottom of the bottle. Other apparatus for removing the tail flashing from a blown container as taught in U.S. Pat. No. 3,677,454 to Boyer, uses a chain and bar mechanism positioned below the dies of the blow molding machines which grasps the tail portion and moves the article up an inclined plane in a direction away from the moving chain. In effect, the tail surface is held and the container forced upward with a tearing motion. In this approach, the container must move through several planes, and changes of direction of motion are required resulting in a complex and expensive equipment. Apparatus for removing flashing such as a dome from the neck of a molded container includes that described in U.S. Pat. No. 3,429,211 to Pelot, which requires a fixed guide and a movable guide gripping the hollow neck while moving the unwanted portion against an adjustable cutting tool obliquely disposed along the direction of travel of the containers. Thus, a special neck design of the bottle is required to utilize this apparatus since a specific type of groove in the neck of the container must be provided to match the fixed and movable guides.